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      Differences in the Kinetics of Dopamine Uptake in Synaptosome Preparations of the Median Eminence Relative to Other Dopaminergically Inervated Brain Regions

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          A comparison of the kinetics of dopamine uptake was made in synaptosomal preparations of the median eminence, striatum and olfactory tubercle. Double reciprocal Lineweaver-Burk plots of the initial velocity versus the concentration of dopamine yielded a single straight line in all three areas. The Michaelis constant (K<sub>m</sub>) in the median eminence (1.8 ± 0.9 × 10<sup>–6</sup> M) was significantly higher (p<0.05) than in the striatum (4.2 ± 0.8 × 10<sup>–8</sup> M) or olfactory tubercle (6.3 ± 1.9 × 10<sup>–8</sup> M). Uptake in the median eminence appeared to be predominantly into dopaminergic terminals since preincubation with desipramine did not affect the maximum velocity (V<sub>max</sub>) of dopamine uptake. Observed uptake was predominantly due to transport across the neuronal membrane and not into storage granules, since reserpine only caused a small decrease in uptake. The low affinity of dopamine uptake in median eminence synaptosomes is consistent with the neurose-cretory nature of these terminals, whereas, in the striatum and olfactory tubercle, high affinity reuptake is consistent with the role of dopamine as a neurotransmitter.

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          Author and article information

          S. Karger AG
          26 March 2008
          : 31
          : 5
          : 316-320
          Department of Obstetrics, Gynecology and Reproductive Sciences, University of California San Francisco, School of Medicine, San Francisco, Calif. and Unité 159 de Neuroendocrinologie, Centre Paul-Broca de l’lnserm, Paris
          123094 Neuroendocrinology 1980;31:316–320
          © 1980 S. Karger AG, Basel

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          Pages: 5
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